Radiation sensitive smoke detector using light conducting means



March 31, 1970 c. A. EATON ETAL 3,50

RADIATION SENSITIVE SMOKE DETECTOR USING LIGHT CONDUCTING MEANS FiledDec. 13, 1967 4 Sheets-Sheet l.-

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RADIATION. SENSITIVE SMOKE DETECTOR USING LIGHT CONDUCTING MEANS FiledD80. 13, 1967 I 4 Sheets-Sheet 2 March 31, 1970 C. A EATON ET 4RADIATION SENSITIVE SMOKE DETECTOR USING LIGHT CONDUCTING MEANS 4Sheets-Sheet :5

Filed Dec. 13, 1967 Ill March 31, 1970 c. A. EATON EI'AL 3,504,184

RADIATION SENSITIVE SMOKE DETECTOR USING LIGHT CONDUCTING MEANS 4Sheets-Sheet 4 Filed Dec. 13, 1967 United States Patent U.S. Cl. 250-2182 Claims ABSTRACT OF THE DISCLOSURE Smoke detection apparatus includinga visual smoke detector comprising a dark chamber providing an air path,a light-carrying rod, such as a glass fibre light guide, for Conveyinglight from a light source and for causing this to pass along a lightpath through the air path, and a window through which the light path maybe viewed.

In an arrangement such as that described in the abstract when even asmall amount of smoke is entrained in the air passing through the airath a viewer looking through the window will see light reflected bysmoke particles passing through the light path.

A second light-carrying rod may be provided spaced by a small gap fromthe end of the first-mentioned rod, the said gap constituting the lightpath. This second rod preferably carries the light received from thefirst rod to provide a source of illumination for a second smokedetector. This second smoke detector preferably incorporates a lightsensitive electric cell.

The second smoke detector may conveniently comprise two light pathslying between and extending respectively from the said light source andthe said electric cell and being mutually inclined so that the saidelectric cell is masked from the light source, the arrangement beingsuch that when smoke particles are present at the intersection betweenthe two light paths, these smoke particles cause light from the lightsource to be deflected on to the light sensitive electric cell.Preferably, the said light paths are inclined to each other by an obtuseangle, preferably 120 or greater and in a preferred embodiment 150.Preferably, the light paths are formed in a block so arranged that theintersection of the light paths take place at a location spaced from theblock, the block preferably having a flat surface located between thelight paths. The smoke detection apparatus preferably comprises a singlehousing for both detectors.

Preferably the apparatus comprises a plurality of units, there being asingle source of light to which the remote ends of the said first rodsare exposed.

An embodiment of the invention will now be described, by way of example,with reference to the accompanying drawings.

In the drawings:

FIGURE 1 is a perspective view of a system comprising two banks of unitsof the invention,

FIGURE 2 is a side view of the system of FIGURE 1 with side walls of theapparatus housing removed,

FIGURE 3 shows the light source for one bank,

FIGURE 4 is the front view of smoke detection unit of the invention,

FIGURE 5 is a section on line 5-5 of FIGURE 4,

FIGURE 6 is a section on line 66 of FIGURE 5, and

FIGURE 7 is a circuit diagram showing the main circuit and the circuitfor one unit.

Referring now to FIGURES 1, 2 and 3, there is shown two banks ofupwardly inclined smoke detection units 10 for use in a ship and twolight sources 11. Each light ice source 11 comprises a quartz iodineaxial filament lamp 12. The lamp 12 is located in a light-proof housing13 (see FIGURE 3) having a hinged door 14 (see FIGURE 2) for removal ofthe lamp 12. A plurality of rods 15, one for each unit 10 in a bank,have their ends (hereinafter called their remote ends) opening into thehousing 13. These rods 15 may be made of glass or Perspex (registeredtrademark) or may preferably be fibre optical rods. The other (or innerend) of each rod 15 is connected to a union 16 secured into the upperwall of the housing of a smoke detection unit 11.

The housing 17 of each detector unit comprises front, rear, top andbottom walls 17a, 17b, 17c and 17d respectively. Two intermediate walls17e and 17 are also provided parallel to the top and bottom walls. Thefront wall 17a is the widest wall, the intermediate walls 172 and 17]being slightly less wide but wider than the remaining walls. Theintermediate walls 17e and 17 slot into recesses in the side walls ofthe cabinet 18 to form an air and lighttight seal therewith.

The rear wall 17!; of the housing 17 has an air inlet socket 19 andabove it an air outlet socket 21. The inlet socket 19 is connected bymeans of a flexible pipe 22 (not shown) to a hold of the ship. Theoutlet socket 21 is connect'ed by a conduit 22 to a header chamber 23common to each bank. A suction pump 20 applies suction pressure to eachheader chamber 23. The outlet from the pump 20 is connected by athree-way valve either to a sniffer pipe which opens in the ships wheelhouse or to an exhaust pipe.

Internally the housing 17 of each unit has a matt black non-reflectivefinish. The housing 17 which is preferably a fabricated steel housing,although it could be a plastics casting, defines an air path connectingthe two sockets 19 and 21. The air path comprises a lower horizontalpath 27 between walls 17d and 17 1 leading from the inlet connection 19;an upper mainly horizontal path 28 between walls and 17e leading to theoutlet connection 21; and vertical connecting path 29 leading from asquare aperture 30 in the wall 17 to upper horizontal path 28. A tubularsighting duct 31 opens into the upper path 28 and is closed off by anangled glass window 32.

The union 16 is, as described above, secured to the top wall 170 of thehousing 17 and is located close to the outlet connection 21. A secondrod 33, which is similar to rod 16, has an end aligned with the innerend of the rod 15 in the intermediate wall 17e. Short lengths of tubing34 are provided on and extending slightly beyond the projecting ends ofthe rods 16 and 33 so that these ends are not visible through thesighting duct 31. The gap between the ends of the rods 15 and 33provides a first smoke detector as will be described in detail below.

An air-flow indicator, in the form of three flexible nylon wands 36,which are white or any other bright colour, is located close to the airoutlet 21. When air passes along the air path, the nylon wands 36 aredeflected from their vertical position and wave in the air flow.

The second rod 33 leads to a second smoke detector 37. This smokedetector 37 comprises a block 38 in which are formed two light passages39 and 40. The light passages 39 and 40 open in a projection 41 of theblock 38 which is located in an aperture in wall 17a. These lightpassages 39 and 40 are inclined to the wall 17f by a small angle ofabout 15. The continuation of the light passages 39 and 40 meet a shortdistance before the front face of the block leaving a small flat plateau42 between the light passages 39 and 40. This plateau 42 prevents dustlodging at the intersection of the light passages. The second rod 33terminates short of the surface 38. At the outer end of the lightpassage 41, there is provided a cadmium disulphide, photo resistivelight sensitive cell 43. Light from the rod 33 enters the passage 39remote from plateau 42 and on leaving this passage 39 will normally beabsorbed by the matt black upper surface of wall 17d or will bereflected into and absorbed by the vertical connecting path 29. Normally(i.e. when there is no smoke) no light is deflected into the passage 41so that the light sensitive cell 43 is in total darkness. This cell 43is connected to a circuit associated therewith, the circuit plate 44 ofwhich is mounted above the block 38. A slot-in connector 45 is mountedon the rear Wall 1712 of the container to connect the circuit to themain power and alarm circuit. A zone indicator light 46 is mounted onthe front wall 17a, and connected to the unit circuit.

The unit circuit Cr of the cell 43 (LC) is shown in FIGURE 5. The cellLC is connected to the variable outlet of a 1 megohm potentiometer P andthrough an 0.1 megohm resistor Res to the base of one transistor T of aDarlington pair. The common collector is con nected to a relay R Thisrelay R controls a relayswitch RS connected in across the supply inseries with the zone indicator light 46. The relay switch R8 is alsoconnected to the main alarm system through a diode D.

The unit circuit is fed from a common stabilised power supply circuit.Mains power is fed to the primary of an input transformer having a 24 v.and a 40 v. secondary winding SW and SW One winding SW has two lamps 12connected thereacross. A relay R is connected in parallel with the lamps12. A pair of relay switches R 8 and R 8 are provided across the lamppair. These switches normally, i.e. when the relay R is energised,connect the lamps 12 to the winding SW The other winding SW is connectedto a rectifier bridge B. A smoothing capacitor C extends across thebridge output. Connected to the negative line is a Zener diode Zconnected via a K ohm resistor R to the positive line. The junction ofthe Zener diode Z and resistor R is connected to the base of thetransistor T and to a capacitor C leading to the negative line. Thetransistor collector leads to the positive line and the emitter isconnected to the positive line and through a capacitor C to the negativeline. In the negative and positive lines are two relay switches R 8 andR 8 respectively. When the relay R is energised these switches connectthese lines to the bridge B.

The relay switches R 5 R 8 R 8 and R 5 are two position switches. Whenthe relay is de-energiscd, as on mains power failure, these switchesconnect the lamps and the power lines of the supply circuit in parallelto a standby battery unit By.

When light falls on the cell LC (43) as will be described its resistancefalls sharply causing the Darlington pair to conduct. This results inthe relay switch R 5 being closed lighting the zone lamp 46 andenergising the main relay R which causes the main fire alarm to beactivated.

A shut-01f butterfly valve 49 is provided to seal off the aperture 30thereby preventing flow through the vertical path 29. A handle 51 islocated on the front face 52 of front wall 171: for controlling theposition of the valve 49. This valve 49 is provided to isolate a holdcontaining a substance, such as cement, which will not burn but whichgives oif dust that will be sucked through the apparatus causing thealarm to be given and the apparatus to be dirtied.

The valve 49 is movable by the handle 51 from a fully open to a fullyclosed or sealed position. The valve 49 may also be adjusted to lie inthe continuation of the light path 39 to reflect light into the lightpath 41 so as to test the operation of the apparatus.

A conventional fault circuit is connected to the lamp 12 to give a faultsignal should this lamp fail.

In use, the units connected to holds containing nonburning and dustysubstances are shut off by their'valves .4 49, the three-way valveconnects the pump outlet to the sniffer pipe, the common lamps 12 areilluminated, and the suction pump 20 is operating. The nylon wandair-flow indicator 36 will wave in the air flow so that a viewer cancheck that air is passing through the air path in each housing. Whilethere is no smoke to be detected, the cells 43 will remain in darknessand the circuits will give no signals.

Should fire or smouldering commence in one of the holds, the smoke givenoil will be drawn through the air path of the associated detector unit11. When the smoke particles pass along lower path 27 through thecontinuation of the light passage 39, these particles will deflect lightinto passage 41 causing this light to fall on the cell 43. This willhave the effect of decreasing the resistance of the cell 43 causing theDarlington pair to conduct energising the relay R; with the result thatthe alarm signal will be emitted. The smoke particles when passingthrough the gap between the rods 16 and 33 will also reflect light whichis visible through the sight ing duct 31. The ofiicer in the wheel househaving been warned by the alarm signal can now make a visual check bylooking through the appropriate sighting duct 31.

The electric and the visual indications of smoke will be given by theapparatus at very low smoke concentra tions. We have found that thefirst or visual detector will give an indication of smoke at as low aconcentration as two percent obscuration per foot Whilst the electric orsecond detector is even more sensitive. Thus remedial fire fightingaction can be taken at a very early stage.

The first or visual detector provided by the gap between the rods 15 and33 also serves to actuate the second or electric detector at low smokeconcentrations as will now be described. The light leaving the inner endof the rod 16 disperses in the shape of a cone. Of this cone of lightonly the central cylindrical part falls on the end of the rod 33. Theremaining part of the cone of light, which part is herein defined as thecone annulus, does not fall on the end of the rod 33. When there is alow concentration of smoke particles in the air drawn into the air path,these particles, when in the cone annulus, will reflect light on to theend of the rod 33. Thus more light will pass from the light passage 39and the scatter light falling on the cell 43 will likewise increase.This in turn will reduce the resistance of the cell 43, causing theDarlington pair to fire so that the alarm signal will be given in theunlikely event it has not already been given.

The invention is not limited to the precise constructional detailshereinbefore described and illustrated in the drawings. For example, theblock 38 may be recessed at the commencement of the light path. Thusscatter light leaving the end of the rod 33 will be absorbed in therecess to a substantial extent and will not be reflected down the path39. Instead of the tubing 34, low ridges may be provided to mask theends of rods 15 and 33. A flashing zenon light, flashing every fiveseconds, may replace the quartz iodine lamp. The apparatus can also beused in a building where a number of rooms or zones are being policed bythe fire detection apparatus.

We claim:

1. Smoke detection apparatus in which a stream of air,

possibly carrying smoke particles, is passed through a dark chamber,provided with a viewing window, a light source being provided toilluminate any smoke particles in said stream of air to render the samevisible and a light sensitive cell, screened from said light source,being arranged in said chamber to be illuminated by reflected light fromsmoke particles in said stream of air characterised in that the streamof air is moved past one end of a light-carrying rod (15, 33) andthrough a gap in said rod to provide two separate positions at whichsmoke particles in said air stream are illuminated from a com mon lightsource.

2.. Smoke detection apparatus according to claim 1,

5 6 further characterised in that the air stream passes along 2,291,7768/1942 Wager 356207 X a pair of substantially parallel paths (27, 28)through said 2,3 06,588 12/ 1942 Cahusac et al 356-207 X dark chamber,the gap in said light-carrying rod (15, 2,410,104 10/1946 Rainey 25022733) lying in one path (28) and the end of said rod lying 2,892,3786/1959 Canada 250218 X adjacent the second path (27), the portion (33)of said 5 3,045,223 7/1962 Kapany et a1 250-227 X light-carrying rodbeing bent between said paths so as 3,168,218 2/1965 Funk et a1. 250218X to direct light obliquely into said second path (27), the

light sensitive cell (43) being adjacent to the end of light- WALTERSTOLWEIN, Primary Examiner carrying rod portion (33), but shielded fromthe beam of light emitted therefrom. 10

-22 2 References Cited 250 340 37 UNITED STATES PATENTS 2,256,595 9/1941Metcalf 250227

